Filter device

ABSTRACT

A filter device, having a filter housing (2) in which an exchangeable filter element (14) is accommodated, is characterized in that the filter element (14) has a securing device (58) that can be inserted axially into a receiving device (20) of the filter housing (2), in that, after a rotational motion has been performed, snap means (70) are used to snap the securing device (58) to the receiving device (20) in a snap position.

The invention relates to a filter device, having a filter housing inwhich a replaceable filter element is accommodated. More specifically,the invention relates to a return filter device provided for in-tankinstallation.

Filter devices of this type are state of the art, cf. DE 10 2015 007 691A1. The space-saving installation in a hydraulic tank renders suchfilter devices suitable for use in compact hydraulically driven deviceswhere there is little available installation space. The in-tankinstallation also permits a simple structure of the filter housing,formed by a cover that can be removably attached to the flange of a tankopening and a relatively thin-walled pipe extending at a distance fromthe filter element from the cover into the interior of the tank to aposition lower than the operational fluid level.

Based on this prior art, the invention addresses the problem ofproviding a filter device of the type regarded above, which ischaracterized by an improved and safe operating performance whilemaintaining the advantages achieved in the prior art.

According to the invention said problem is solved by a filter devicehaving the features of claim 1 in its entirety.

According to the characterizing part of claim 1, an essential feature ofthe invention is the filter element having a securing device that can beinserted axially into a receiving device of the filter housing, wherein,after a rotational motion has been performed, snap means are used tosnap the securing device to the receiving device in a snap position.Preferably, provision is made that in the snap position, while forming alock, in particular against axial disassembly, contact surfaces of thesecuring device and of the receiving device, which are assigned to eachother in pairs, are in contact with each other when the device is not inoperation. In this way, at least when the device is not in operation,the filter element is secured axially downwards in its functionalposition in the filter housing under the effect of its weight, whereinthe radially acting frictional force between the said contact surfacesalso counteracts any radial disassembly. This mutual contact, achievedby a rotational motion into the snap position, provides a form-fittingengagement to secure the securing device and the receiving deviceagainst axial forces acting at least downwards in the lift-offdirection. The snap means effective in the snap position, secure thesecuring device and the receiving device to each other in the rotationalposition of form-fitting engagement of the contact surfaces.

In a preferred embodiment of the filter device according to theinvention, provision is made that at least one further pair of contactsurfaces in the form of a guide surface on the securing device and afurther guide surface on the receiving device now secures the filterelement against its weight force by contact of the guide surfaces toeach other during operation of the filter device under the fluidpressure produced. Because of this surface limitation, the motion of thefilter element during operation of the device is also counteractedaxially upwards, wherein again the friction between said surfaces hasthe effect that the filter element is likewise secured againstunintentional radial disassembly. In this respect, the contact betweenthe above-mentioned contact surfaces is then relieved of the securingdevice and of the receiving device.

In advantageous exemplary embodiments, the securing device can beinserted into the receiving device of the filter housing against theforce of an energy storage acting on the filter element. In addition tothe snap means, the force closure at the contact surfaces generated bythe action of the energy storage forms an additional safeguard againstrotation from the snap position, so that a particularly securepositional fixing of the filter element is ensured in any operatingstate of the device.

Advantageously, the arrangement may be such that the securing device ispart of an end cap of the filter element, wherein said securing devicehas securing bars projecting axially from the end cap, wherein saidsecuring bars have the assignable snap means and a part of the contactsurfaces. Advantageously, the receiving device can be part of a coverforming a housing part of the tank filter, wherein said cover can beattached to the tank flange of a tank opening.

The snap means can be formed by snap hooks projecting radially beyondthe axial orientation of the securing bars and springing back andengaging with assignable snap recesses in the receiving device in thesnap position, requiring low actuation forces.

In advantageous exemplary embodiments, the receiving device hasguideways, which, following a predeterminable course of curvature, guidethe filter element inserted axially into the filter housing during itsrotational motion until it reaches the snap position, preventingoperational errors.

Advantageously, the arrangement can be made in such a way that theguideways each have an interruption for the passage of an assignablesnap-in hook each when the filter element is inserted axially, whichcontributes to a fail-safe assembly.

At least some of the interruptions can have a control surface, whichlifts the respective snap hook during the rotational motion out of theinterruption for its further travel into the snap position, which alsofacilitates the self-explanatory assembly.

In this case, the arrangement can advantageously be made in such a waythat, during continued rotational motion after the respective snap hookhas been lifted out of the assigned interruption, the snap hook passesover a further guide part which, projecting radially outwards from acurved path, also supports the snap hooks in their snap position. Inthis way, a particularly secure snap-fit connection is achieved.

The further guide part can as a hollow box be integrally formed on therespective guideway, wherein the guide part engages with a further,additional guide surface in an axial clearance between the snap hook andthe contact surface of the securing bar, which helps to support theguiding process until the snap-fit connection is achieved and ensuresthat the element does not unintentionally fall out of the holder in theaxial direction.

In advantageous exemplary embodiments, when the rotational motion intothe snap position of the filter element in the assigned filter housingis completed, the respective snap hook engages with a recess in theguideway, which adjoins the respective further guide part in thedirection of rotation associated with this rotational motion.

In particularly advantageous exemplary embodiments, the energy storage,formed as a compression spring, is a component of a bypass valve, theclosing part of which preloads the filter element in the oppositedirection to its axial insertion motion.

The invention is explained in detail below with reference to anexemplary embodiment shown in the drawing.

In the Figures:

FIG. 1 shows a perspective oblique view of an exemplary embodiment ofthe filter device according to the invention;

FIG. 2 shows, sectioned in a vertical plane, a perspective oblique viewof the exemplary embodiment;

FIG. 3 shows a perspective oblique view of the separately depictedfilter element of the exemplary embodiment;

FIG. 4 shows an oblique perspective view of the exemplary embodimentsectioned in the area of the cover in a horizontal sectional plane,wherein interacting parts of the cover and filter element are shown inthe position at a first stage of the insertion process;

FIGS. 5 and 6 are corresponding to FIG. 4, wherein the positions at asecond and a third stage of the insertion process, respectively, areshown; and

FIG. 7 shows a perspective oblique view of the part of the exemplaryembodiment adjoining the cover, drawn on a larger scale and sectionedwith a vertical sectional plane.

With reference to the accompanying drawings, the invention is explainedusing the example of a return filter intended for installation in a tank(not shown). The exemplary embodiment has a filter housing designated asa whole by the reference numeral 2, which is formed by a cover 4 and anoutlet pipe 6. The cover 4 has a male thread 8, which can be used toscrew it to a tank flange 10, which is located at a tank opening of thetank not shown. The upper end of the discharge pipe 6, in the form of athin-walled hollow cylinder, rests against the inside of the cover 4. Inthis case, a fastener can be provided at the cover 4, or the pipe 6 canbe secured to the cover 4 by a support from the lower end 12. The outletpipe 6, which encompasses a filter element 14 inserted in the housing 2at a radial distance, has windows 16 for the outflow of filtrate,wherein said windows 16 are arranged on the pipe 6 at such a height thatthe filtrate flows out into the tank at a height that favors degassingeven for a small tank volume. As indicated in FIG. 2 by several overlappoints 18, the outlet pipe 6 can be composed of several pipe segments,which can be used to implement filter housings 2 of desired lengths.

The interior 20 of the cover 4, wherein said interior 20 has the shapeof a circular, flat bowl, forms the receiving device for the filterelement 14, which is shown separately in FIG. 3. Between an upper endcap 22 and a lower end cap 24, the filter element 14 has ahollow-cylindrical filter medium 26 that encompasses an inner filtercavity 28 on the inside and is supported by a support tube 30 on itsoutside. The support tube, formed from a plastic grid structure, iscomposed of tube segments 30, similar to the outlet pipe 6, wherein saidtube segments 30 are interconnected at joints 32. As is most clearlyshown in FIGS. 2 and 3, the lower end cap 24 has three circumferentiallydistributed foot parts 34 that project axially downward and obliquelyoutward. The circumferential rim of the foot parts 34 form a stopsurface 36 for supporting the lower end 12 of the outlet pipe 6. Thelower end cap 24 forms the inlet cap for the filter operation and has acentral opening 38 through which a return connector 40 passes, throughwhich unfiltered matter passes to the inner filter cavity 28. A movablecap 42 extends above and beyond the inner end of the connecter 40,wherein said cap 42 forms a check valve that prevents back contaminationinto the tank during maintenance operations. Wall segments 44 extendingupwards from the circumferential area of the lower end cap 24, formguides for the lower support tube segment 30.

The top of the upper end cap 22 is formed by a flat circular disc 46,which is closed except for a central opening 48, the rim 50 of whichforms the sealing seat for the closing body 52 of a bypass valve. Incorrespondence to the rim segments 44 on the lower end cap 24, rimsegments 56 (FIG. 3) forming the guide for the upper support tubesegment 30, extend downward from the circumferential rim 54 of the endcap 22, wherein said circumferential rim 54 forms the enclosure for thefilter medium 26 and the upper support tube segment 30. The upper endcap 22 comprises a securing device that interacts for positionallyretaining the filter element 14 in the installed functional positionwith a receiving device located in the interior 20 of the cover 4. Thesecuring device is formed by three securing bars 58 which, see FIG. 3,are offset from one another by 120° and extend near the circumferentialrim 54 upwards away from the circular disc 46. For interaction with thesecuring bars 58, the receiving device has guide tracks and guide parts,which are integrally formed in the interior 20 of the cover 4 on the topwall 60 thereof, which extend therefrom in the direction of the filterelement 14 and which form guide tracks and guide parts. The process ofinstalling a filter element 14 is performed in stages, wherein the firststage is inserting the end cap 22 into the interior 20 in an axialmotion. Insertion takes place with the filter element 14 in a rotationalposition, in which the securing bars 58 are each aligned with aninsertion space 63, which are free spaces in the interior 20 offset fromone another by 120°. The filter element 14 is then rotated in twofurther stages until it reaches a snap position. During this rotarymotion, the securing bars 58 are guided by arc parts 78 (FIGS. 4 to 6)and guide parts. The axial insertion motion occurs against the springforce of a compression spring 62, which is clamped between the top wall60 and the closing body 52 of the bypass valve and presses the closingbody 52 into the closed position at the rim 50 of the opening 48 of theend cap 22, wherein said rim 50 forms the sealing seat.

As shown in FIG. 3, the securing bars 58 have, adjacent to the circulardisc 46 of the end cap 22, a foot 64 in the form of a cylindrical shellpart, the upper surface of which is delimited by a guide surface 66extending in a radial plane. From one end of the guide surface 66, andoffset radially outwards with respect thereto, a wall part 68 extendsupwards from the guide surface 66 in the axial direction and merges witha snap hook 70, which extends along the guide surface 66 and beyond theend of it, while forming an axial clearance. The wall part 68 forms acontact surface 72 with the underside located below the guide surface66, wherein said contact surface 72, in the snap position shown in FIG.7, in conjunction with a contact surface 74 of the receiving device,forms a pair of blocking surfaces interacting in a form-fitting mannerwith each other, wherein said pair of blocking surfaces prevents thefilter element 14 from moving axially downwards as viewed in thedirection of FIG. 7.

Provision is further made that at least one further pair of contactsurfaces in the form of the guide surface 66 on the securing device 58and a further guide surface 76 on the mount 20 is provided. These nowprovide, in particular during operation of the device under theresulting fluid pressure, for the filter element 14 to be securedagainst its weight force by the contact of said guide surfaces 66, 76with each other. By this limitation of the surface, the motion of thefilter element 14 during operation of the device is also counteredaxially upwards when viewed in the direction of FIG. 7. A correspondingfriction between said pairs of surfaces 72, 74; 66, 76 causes the filterelement 14 to be equally secured within the filter housing 2 against anyunintentional radial disassembly.

FIG. 4 shows the situation during the first stage of the installationprocess of the filter element 14. In this insertion-rotation position,the snap hooks 70 are located in the region of an interruption 77 eachof a main guideway formed by the arc parts 78, wherein said mainguideway forms the guide for the snap hooks 70 during the rotationalmotion. The interruptions 77 provide in the interior 20 of the cover 4the insertion space 63 as a free space for the axial insertion motion ofthe securing bars 58 with the snap hooks 70, such that a rotationalposition is predetermined for the insertion motion as the first stage ofthe installation process. At each of the interruptions 77, a controlsurface 80 each forms the transition to the next arc part 78, whereinthe control surface 80 has the shape of a ramp sloping radiallyoutwards.

During the second stage of the installation process, in which the filterelement 14 is rotated (clockwise when viewed in the direction of FIGS. 4to 6), a front control bevel 81 of the snap hooks 70 contacts therespective control surface 80 and thus the snap hooks 70 are liftedradially outwards out of the interruption 77. FIG. 5 shows therotational position in which the snap hooks 70 interact with therespective control surface 80 for this purpose. Upon further rotationalmotion, as the third stage of the installation process, the snap hooks70 are guided on the outside of the adjoining arc part 78 until theyreach the snap position shown in FIG. 6, in which a latch 83, formedbehind the control slope 81, of the rebounding snap hooks 70 engages ina snap recess 82, thus securing the rotational position in the snapposition. During motion between the positions shown in FIGS. 5 and 6, inwhich the snap hooks 70 are guided on the outside of the arc part 78until they reach the snap recesses 82, the snap hooks 70 pass over afurther guide part formed by one block 84 each integrally formed on thetop wall 60, which forms a kind of hollow box having an inner recess, inwhich the outer contact surface 74 and an upper guide body 90 arelocated as axial boundaries of the cavity, see FIG. 7.

When the snap position is reached, FIG. 6, the snap hook 70 has overrunthe block 84. At the same time, the contact surface 72 and a guidesurface 86, extending at a distance along the snap hook 70, of the parts68 projecting radially outwards from the foot 64 of the securing bars 58have moved into the cavity in the block 84, such that in the snapposition the form-fitting engagement shown in FIG. 7 is formed, in whichthe abutting contact surfaces 72 and 74 form the safeguard against axialdownward forces, the surfaces 66 and 76 form the safeguard against axialupward forces and thus form the barrier against axial disassembly inboth directions. Because of the acting spring force of the compressionspring 62 of the bypass valve, the contact surfaces 72, 74 are also inforce-fit contact with each other in the snap position, so that inaddition to the snap engagement of the snap hooks 70 with the recesses82, a further safeguard against rotation is formed, which has to beovercome for the removal of the filter element 14. Foot parts 34projecting downwards from the lower end cap 24 are provided as a rotaryaid for installation and removal of the filter element 14.

1. A filter device, having a filter housing (2) in which an exchangeablefilter element (14) is accommodated, characterized in that the filterelement (14) has a securing device (58) that can be inserted axiallyinto a receiving device (20) of the filter housing (2), in that, after arotational motion has been performed, snap means (70) are used to snapthe securing device (58) to the receiving device (20) in a snapposition.
 2. The filter device according to claim 1, characterized inthat in the snap position, while forming a lock, in particular againstaxial disassembly, contact surfaces (72, 74) of the securing device (58)and the receiving device (20) are in contact with each other when thedevice is not in operation.
 3. The filter device according to claim 1,characterized in that at least one further pair of contact surfaces inthe form of a guide surface (66) on the securing device (58) and afurther guide surface (76) on the receiving device (20) secures thefilter element (14) against its weight force by contact of the guidesurfaces (66, 76) to each other during operation of the filter deviceunder the fluid pressure produced.
 4. The filter device according toclaim 1, characterized in that the securing device (58) can be insertedinto the receiving device (20) of the filter housing (2) against theforce of an energy storage (62) acting on the filter element (14). 5.The filter device of claim 1, characterized in that the securing deviceis part of an end cap (22) of the filter element (14), wherein saidsecuring device has securing bars (58) projecting axially from the endcap (22), wherein said securing bars (58) have the assignable snap means(70) and a part (72) of the contact surfaces (72, 74).
 6. The filterdevice according to claim 1, characterized in that the snap means areformed of snap hooks (70) projecting radially beyond the axialorientation of the securing bars (58) and springing back and engagingwith assignable snap recesses (82) in the receiving device (20) in thesnap position.
 7. The filter device according to claim 1, characterizedin that the receiving device (20) has guideways (78) which, following apredeterminable course of curvature, guide the filter element (14)inserted axially into the filter housing (2), during its rotationalmotion until it reaches the snap position.
 8. The filter deviceaccording to claim 1, characterized in that the guideways (78) each havean interruption (77) for a passage of an assignable snap-in hook eachwhen the filter element is inserted axially.
 9. The filter deviceaccording to claim 1, characterized in that at least part of theinterruptions (77) have a control surface (80), which move therespective snap hook (70) into the snap position during the rotationalmotion for its further travel.
 10. The filter device according to claim1, characterized in that, during continued rotational motion after therespective snap hook (70) has been lifted out of the assignedinterruption (77), the snap hook (70) passes over a further guide part(84) which, projecting radially outwards from a curved path, alsosupports the snap hooks (70) in their snap position.
 11. The filterdevice according to claim 1, characterized in that the guide part (84)as a hollow box is integrally formed on the respective guideway (78),and in that the guide part (84) engages with a further third guidesurface (90) in an axial spacing between the snap hook (70) and thecontact surface (72) of the securing bar (58).
 12. The filter deviceaccording to claim 1, characterized in that, when the rotational motioninto the snap position of the filter element (14) in the assigned filterhousing (2) is completed, the respective snap hook (70) engages with arecess (82) in the guideway (78) which adjoins the respective guide part(78) in the direction of rotation associated with this rotationalmotion.
 13. The filter device according to claim 1, characterized inthat the energy storage, formed as a compression spring (62), is acomponent of a bypass valve, the closing part (52) of which presses thefilter element (14) in the opposite direction to its axial insertionmotion.